Interest in developing nanocomposites with improved performance properties has increased since the discovery of carbon nanotubes. Carbon nanotubes are known to exhibit desirable properties, depending on their configuration, such as high strength per unit mass, electrical conductivity, thermal conductivity, and luminescence upon irradiation. In particular, carbon nanotubes are attractive for incorporating into composite materials as reinforcement additives, for example, plastics.
As with any composite, it is highly desirable to obtain as close to a homogeneous dispersion of additives as possible to achieve uniform characteristics throughout a material. Previous attempts to incorporate carbon nanotubes into other materials to create composites have tended to meet with limited success due to their poor dispersity. Techniques such as ultrasonication, surfactants, polymer wrapping, and sidewall functionalization have not produced a level of homogeneous blending, improved tensile strength, or modulus characteristics as expected. Typically during production, carbon nanotubes in solvent or other materials tend to aggregate and entangle into a dense, robust network of “ropes” 10-50 nm in diameter and up to μm's in length due in part to strong van der Waals force attraction between tubes. Further, it has been difficult to match desirable solvent characteristics with both carbon nanotubes and other materials, rendering carbon nanotubes difficult to blend with other materials, such as polymers.
There remains a need for techniques that provide carbon nanotubes that are homogeneously dispersible with other materials so as to produce uniform composites, particularly those that are strong and light.